<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>javascript</title>
  <style>
    * {
      margin: 0;
      padding: 0;
      box-sizing: border-box
    }
    body {
      font-size: 14px;
      padding: 20px;
    }
    ul li {
      line-height: 30px;
    }
  </style>
</head>
<body>
  <ul>
    <li></li>
  </ul>
</body>
<script src="https://cdn.bootcss.com/vue/2.6.8/vue.js"></script>
<script>
    var a = 123;
    console.log(typeof a)
    console.dir(Number)
    console.log(a.toString(10))
    console.log(1 + '2') // number + string类型时，会把number转化为str
    console.log(1 + true) // number + boolean类型时，会把boolen类型转化为number类型
    console.log('12' + true) // string + boolean类型时，会把boolean转化为string类型
    console.log(12 - '10')
    console.log('56' - '6')
    console.log(10 - true)
</script>
</html>